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NEET-XII-Physics

40: Electromagnetic Waves

with Solutions - page 2
Qstn# iii-4 Prvs-QstnNext-Qstn
  • #4
    Which of the following have zero average value in a plane electromagnetic wave?
    (a) Electric field
    (b) Magnetic field
    (c) Electric energy
    (d) Magnetic energy
    digAnsr:   a,b
    Ans : (a) Electric field
    (b) Magnetic field
    In a plane electromagnetic wave, the electric and the magnetic fields oscillate sinusoidally. For an electromagnetic wave propagating in the z-direction, the electric and magnetic fields are given by:
    Ex = E0 sin (kz - ωt)
    By = B0 sin (kz - ωt)
    These are sinusoidal functions. Therefore, for a fixed value of z, the average value of the electric and magnetic fields are zero.
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